题解 | 最差是第几名(二)

select grade from (select grade,(select sum(number) from class_grade) as total,
        sum(number) over(order by grade) a,
        sum(number) over(order by grade desc) b
        from class_grade) t1
where a >= total/2 and b >=total/2
order by grade;

没想出来，核心思路是通过正序和逆序的累计分布交叉定位中位数区间